US 2009/0278350 A1 is known. There, a synchronous generator with e.g. 20 windings is connected to a two-stage direct converter. During the start-up of the turbine, a number of windings of the generator are combined in order to increase the voltage at the windings. With the aid of this higher voltage, the generator may be operated to function as a motor and to increase the rotational speed of the turbine. During normal operation, the output current of the converter is controlled to a desired sinusoidal shape.
It is known to couple a filter circuit to the output of a converter. With the help of this filter circuit, it is possible to smooth the output current of the converter. However, standard filter circuits are bulky and costly.